Suppose you begin with 1.50~g of the hydrate copper(ii)sulfate · x-hydrate (cuso4· x h2o), where x is an integer. after dehydration you find that you are left with 0.96~g of the an-hydrate cuso4. what is the unknown integer x. round your answer to the nearest integer, enter only an integer.
suppose you begin with of the hydrate kal(so4)2 · 12h2o. after dehydration you find that you are left with 3.0~g of the an-hydrate kal(so4)2. how many grams did you start with? write the value to the correct number of significance figures.

These are two questions and two answers.

Question 1.

x = 5

Explanation:

1) Data:

m₁ = 1.50 g

compound₁: CuSO₄· x H₂O

m₂ = 0.96g

compound₂ = CuSO₄

x = ? (round to the nearest integer)

2) Solution:

i) molar mass of CuSO₄ = 63.546g/mol + 32.065g/mol + 4×15.999g/mol = 159.607g/mol

ii) number of moles of CuSO₄

number of moles = mass in grams / molar mass = 1.50 g/ 159.607 g/mol = 0.006265 mol

iii) molar mass of H₂O = 18.015 g/mol

iv) mass of H₂O = 1.50g - 0.96g = 0.54g

v) number of moles of H₂O = mass in grams / molar mass = 0.54 g / 18.015 g/mol = 0.0300 mol

vi) Ratio moles H₂O / moles CuSO₄ = 0.0300 / 0.0062625 ≈ 5

∴ x = 5.

Question 2.

5.5 g

1) Data:

compound₁ = KAl(SO₄)₂ · 12H₂O.

compound₂ = KAl(SO₄)₂

m₂ = 3.0 g KAl(SO₄)₂

m₁ = ? (two significant figures)

2) Solution:

i) molar mass of KAl(SO₄)₂ = 39.098g/mol + 26.982g/mol + 2×32.065g/mol + 8×15.999g/mol = 258.202

ii) number of moles of KAl(SO₄)₂ = mass in grams / molar mass = 3.0g / 258.202 = 0.011619 mol

iii) number of moles of H₂O = 12 × number of moles of KAl(SO₄)₂ = 12 × 0.011619*12 mol = 0.1394 moles

iv) mass of H₂O = number of moles × molar mass = 0.1394 moles × 18.015 g/mol = 2.5 g (rounded to two significant figures)

v) mass of the original compound = mass of KAl(SO₄)₂ + mass of H₂O = 5.5g

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: